Shape Grammar

The Shape Grammar formalism, developed in the 1970's
by George Stiny and James Gips, was inspired by the rewrite grammars
of Chomskyan formal language theory. It differs from classical rewrite
grammars in two respects:
(1) The distinction between terminal and non-terminal symbols is abolished.
The symbols that are rewritten are the same symbols that occur in the
final design.
(2) It is claimed that the symbols that are rewritten are geometrical
entities (for instance: line segments) rather than discrete symbols
that represent such entities.

The earliest Shape Grammars worked with line segments, but extensions
were developed that deal with color and with three-dimensional shape.